1. Field of the Invention
The present invention relates to an isolation structure of a photoelectric conversion apparatus.
2. Description of the Related Art
Many digital still cameras and digital camcorders use CCD-type or CMOS-type photoelectric conversion apparatuses. In recent years, the pixels of photoelectric conversion apparatuses are being reduced in size, and measures to deal with mixing (cross talk) charges between adjacent pixels that occurs as a result are being studied.
Japanese Patent Application Laid-Open No. 2003-258232 discusses a construction in which a p-type well region that acts as a barrier for element isolation for preventing mixing (cross talk) charges between adjacent pixels is formed in a deep region in combination with an n-type well region of a photoelectric conversion element.
However, even with the p-type well region discussed in Japanese Patent Application Laid-Open No. 2003-258232, there are cases in which it is difficult to adequately suppress the leakage of charges. Further, generally, with photoelectric conversion apparatuses, a transistor for reading out a charge of a photoelectric conversion element is provided at the periphery of the photoelectric conversion element, and it is not necessarily the case that photoelectric conversion elements are disposed at equal distances from each other. The present inventors discovered that in some cases the leakage amounts of charges from p-type well regions can serve as element isolation regions of photoelectric conversion elements disclosed in Japanese Patent Application Laid-Open No. 2003-258232 differ depending on the spaces between the photoelectric conversion elements. When the leakage amounts of signal charges to adjacent photoelectric conversion elements vary in this manner, the image quality decreases and correction of image signals is difficult.